HMS L24

L9 and its successors were enlarged to accommodate 21-inch (53.3 cm) torpedoes and more fuel. The submarine had a length of 238 feet 7 inches (72.7 m) overall, a beam of 23 feet 6 inches (7.2 m) and a mean draft of 13 feet 3 inches (4.0 m).[1] They displaced 914 long tons (929 t) on the surface and 1,089 long tons (1,106 t) submerged. The L-class submarines had a crew of 38 officers and ratings.[2] They had a diving depth of 150 feet (45.7 m).[3]

For surface running, the boats were powered by two 12-cylinder Vickers[4] 1,200-brake-horsepower (895 kW) diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 600-horsepower (447 kW) electric motor.[1] They could reach 17 knots (31 km/h; 20 mph) on the surface and 10.5 knots (19.4 km/h; 12.1 mph) underwater. On the surface, the L class had a range of 3,800 nautical miles (7,000 km; 4,400 mi) at 10 knots (19 km/h; 12 mph).[3]

The boats were armed with four 21-inch torpedo tubes in the bow and two 18-inch (45 cm) in broadside mounts. They carried four reload torpedoes for the 21-inch tubes for a grand total of ten torpedoes of all sizes.[5] They were also armed with a 4-inch (102 mm) deck gun.[2]

HMS L24 was built by Vickers at their Barrow-in-Furness shipyard, launched on 19 February 1919, and completed at an unknown date. The boat was sunk with all hands lost in a collision with the battleship Resolution during an exercise off Portland Bill in the English Channel on 10 January 1924.[6] A memorial is located in St Ann's Church in HMNB Portsmouth.[7]

The wreck is located at 50°22.50′N 02°37.79′W at a depth of 52 metres. Her hydroplanes remain set to hard dive, indicating that she was trying to take evasive action. A hatch is open and there is obvious damage where Resolution sliced into her hull. The wreck is designated as a protected place under the Protection of Military Remains Act 1986.

• Akermann, Paul (2002). Encyclopaedia of British Submarines 1901–1955 (reprint of the 1989 ed.). Penzance, Cornwall: Periscope Publishing. ISBN 1-904381-05-7.
• Colledge, J. J.; Warlow, Ben (2006) [1969]. Ships of the Royal Navy: The Complete Record of all Fighting Ships of the Royal Navy (Rev. ed.). London: Chatham Publishing. ISBN 978-1-86176-281-8.
• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships: 1906–1921. Annapolis, Maryland: Naval Institute Press. ISBN 0-85177-245-5.
• Harrison, A. N. (January 1979). "The Development of HM Submarines From Holland No. 1 (1901) to Porpoise (1930) (BR3043)". Submariners Association: Barrow in Furness Branch. Archived from the original on 19 May 2015. Retrieved 19 August 2015.
• Innes McCartney (2002). Lost Patrols: Submarine Wrecks of the English Channel.

• SI 2008/0950 Designation under the Protection of Military Remains Act